Long press where you want to begin copying text. Small blue "handles" should appear. Drag these to include the text you want to copy. You should see an option displayed at the top of your screen to copy the selected text. Go to where you want to paste it and long press there. A small button labeled paste should pop up. Click on it to paste your copied text. At least that's how it works in previous versions of Android. I expect it is the same in Jelly Bean.

Long press where you want to begin copying text. Small blue "handles" should appear. Drag these to include the text you want to copy. You should see an option displayed at the top of your screen to copy the selected text. Go to where you want to paste it and long press there. A small button labeled paste should pop up. Click on it to paste your copied text. At least that's how it works in previous versions of Android. I expect it is the same in Jelly Bean.